<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>clear</title>
    <style>
        .box1{
            width: 100px;
            height: 100px;
            background-color: #bbffaa;
            font-size: 50px;
            float: left;
        }
        .box2{
            width: 200px;
            height:150px;
            background-color: yellow;
            font-size: 50px;
            float:right;
        }
        .box3{
            width: 100px;
            height: 100px;
            background-color: orange;
            font-size: 50px;
            clear: both;
        }
    </style>
</head>
<body>
    <div class="box1">1</div>
    <div class="box2">2</div>
    <div class="box3">3</div>
</body>
</html>